chore(internal): minor streaming updates (#647)

src/core.ts

@@ -44,6 +44,11 @@ async function defaultParseResponse<T>(props: APIResponseProps): Promise<T> {
 
     // Note: there is an invariant here that isn't represented in the type system
     // that if you set `stream: true` the response type must also be `Stream<T>`
+
+    if (props.options.__streamClass) {
+      return props.options.__streamClass.fromSSEResponse(response, props.controller) as any;
+    }
+
     return Stream.fromSSEResponse(response, props.controller) as any;
   }
 
@@ -743,6 +748,7 @@ export type RequestOptions<Req = unknown | Record<string, unknown> | Readable> =
   idempotencyKey?: string;
 
   __binaryResponse?: boolean | undefined;
+  __streamClass?: typeof Stream;
 };
 
 // This is required so that we can determine if a given object matches the RequestOptions
@@ -763,6 +769,7 @@ const requestOptionsKeys: KeysEnum<RequestOptions> = {
   idempotencyKey: true,
 
   __binaryResponse: true,
+  __streamClass: true,
 };
 
 export const isRequestOptions = (obj: unknown): obj is RequestOptions => {

src/streaming.ts

@@ -3,9 +3,9 @@ import { OpenAIError } from './error';
 
 import { APIError } from 'openai/error';
 
-type Bytes = string | ArrayBuffer | Uint8Array | Buffer | null | undefined;
+export type Bytes = string | ArrayBuffer | Uint8Array | Buffer | null | undefined;
 
-type ServerSentEvent = {
+export type ServerSentEvent = {
   event: string | null;
   data: string;
   raw: string[];
@@ -381,7 +381,7 @@ function partition(str: string, delimiter: string): [string, string, string] {
  *
  * This polyfill was pulled from https://github.com/MattiasBuelens/web-streams-polyfill/pull/122#issuecomment-1627354490
  */
-function readableStreamAsyncIterable<T>(stream: any): AsyncIterableIterator<T> {
+export function readableStreamAsyncIterable<T>(stream: any): AsyncIterableIterator<T> {
   if (stream[Symbol.asyncIterator]) return stream;
 
   const reader = stream.getReader();